This invention is particularly useful for the antitheft protection of motor vehicle, construction equipment, and other high value apparatus in which a security system can be housed. While not limited thereto the invention is particularly useful for the protection of apparatus which is normally moved from place to place or is fixed to an immovable structure. If the apparatus to be protected against theft cannot be made secure by enclosure or attachment, it is usual practice to attempt to sense the theft or attempted theft and, on that occasion, to initiate some preventive measure. A common preventative is to sound an alarm capable of attracting attention to the theft. The detection of motion is a logical choice when attempting to provide an apparatus which is applicable to the protection of a wide variety of portable apparatus in a multitude of different situations. However, designing a satisfactory motion sensitive security system is complicated by the need to differentiate between authorized and unauthorized movement. There is a need to provide operating power in a way that prevents defeat of the system and, in a truly universal system, there is a need to devise a sensor which is effective without regard to spacial orientation or temperature differences and other physical factors.
Prior systems have incorporated features to overcome these and other problems for particular applications. Arming switches, self contained power sources, time delay circuitry, and other means have been employed. In general, however, the inclusion of such features to solve a problem peculiar to one application has rendered the system less useful, or even useless, in other applications. The need remains for a sensor and a system which has wide application, and one purpose of the invention is to satisfy that need.